Processing apparatus, method of operating processing apparatus, and operation program for processing apparatus

ABSTRACT

A body thickness conversion unit converts a body thickness from a distance image imaged by a distance measurement camera to acquire the body thickness. A setting unit sets a gradation transformation function for use in gradation transformation processing to a radiographic image corresponding to the body thickness. A radiographic image acquisition unit acquires the radiographic image output from a radiation detector in radioscopy. A gradation transformation processing unit starts the gradation transformation processing with the gradation transformation function set by the setting unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 toJapanese Patent Application No. 2020-098879, filed on Jun. 5, 2020. Theabove application is hereby expressly incorporated by reference, in itsentirety, into the present application.

BACKGROUND 1. Technical Field

A technique of the present disclosure relates to a processing apparatus,a method of operating a processing apparatus, and an operation programfor a processing apparatus.

2. Description of the Related Art

In a medical field, for example, a radioscopy apparatus is used forvarious operations, such as a gastric barium test, cystography, andorthopedic reduction. The radioscopy apparatus continuously irradiates asubject with radiation in a comparatively low dose from a radiationsource and displays radiographic images output from the radiationdetector on a display in a form of video in real time.

In the radioscopy apparatus, suppressing fluctuation of contrast betweenframes of a radiographic image constituting video leads to improvementof diagnosability. For this reason, in the related art, for example, asdescribed in JP2011-005050A, a method that appropriately controls agradation transformation function (referred to as a tone curve) for usein gradation transformation processing of a radiographic image of apresent frame based on a radiographic image of a previous frame tosuppress fluctuation of contrast between the frames has beenimplemented.

SUMMARY

Radioscopy by the radioscopy apparatus is started, for example, in acase where an operator depresses a foot switch with a foot. In a firststage of radioscopy of which the start is instructed by the operatordepressing the foot switch with the foot, there is of course noradiographic image of a previous frame to be referred, and thus, adefault gradation transformation function is used for the gradationtransformation processing. Then, the default gradation transformationfunction is changed by a radiographic image output one at a time throughradioscopy, and finally, becomes an appropriate gradation transformationfunction corresponding to a body thickness of a subject.

Until the default gradation transformation function becomes theappropriate gradation transformation function, in other words, from whenradioscopy is started until the gradation transformation processingbecomes appropriate, video display of the radiographic image is notperformed even though the operator depresses the foot switch with thefoot and the irradiation of the radiation is performed. For this reason,the operator needs to wait for a start of an operation while the videodisplay of the radiographic image is not performed. The foot switch isfrequently operated to repeat irradiation and stop of radiation severaltimes depending on the operation, and thus, such delay makes theoperator feel stress. Accordingly, how to reduce the time needed fromwhen radioscopy is started until the gradation transformation processingbecomes appropriate is an extremely important issue for the radioscopyapparatus.

An object of the technique of the present disclosure is to provide aprocessing apparatus, a method of operating a processing apparatus, andan operation program for a processing apparatus capable of reducing atime needed from when radioscopy is started until gradationtransformation processing becomes appropriate.

To achieve the above-described object, the present disclosure provides aprocessing apparatus that is used for a radioscopy apparatus including aradiation source configured to continuously irradiate a subject withradiation and a radiation detector configured to detect the radiationtransmitted through the subject to output a radiographic image. Theprocessing apparatus comprises at least one processor. The processor isconfigured to acquire a body thickness of the subject measured by a bodythickness measurement sensor, set a gradation transformation functionfor use in gradation transformation processing to the radiographic imagecorresponding to the body thickness, acquire the radiographic imageoutput from the radiation detector, and start the gradationtransformation processing with the set gradation transformationfunction.

It is preferable that the processor is configured to, in the gradationtransformation function, as the body thickness is thinner, increase arange of an output pixel value with respect to a range where an inputpixel value is relatively high, more than a range of an output pixelvalue with respect to a range where an input pixel value is relativelylow.

It is preferable that the processor is configured to, in the gradationtransformation function, as the body thickness is thicker, increase arange of an output pixel value with respect to a range where an inputpixel value is relatively low, more than a range of an output pixelvalue with respect to a range where an input pixel value is relativelyhigh.

It is preferable that the processor is configured to correct a defaultgradation transformation function corresponding to the body thickness togenerate gradation transformation function to be set.

It is preferable that the processor is configured to generate thegradation transformation function having an S-curved shape from thedefault gradation transformation function having a linear shape.

It is preferable that the processor is configured to make the bodythickness measurement sensor measure the body thickness in a case wherethe irradiation of the radiation is not performed.

It is preferable that the processor is configured to make the bodythickness measurement sensor measure the body thickness insynchronization with a timing at which the radiation detector outputsthe radiographic image for offset correction.

It is preferable that the body thickness measurement sensor is adistance measurement camera that outputs a distance image representing adistance to a surface of an object using a time-of-flight system, andthe processor is configured to convert the body thickness from thedistance image.

The present disclosure provides a method of operating a processingapparatus that is used for a radioscopy apparatus including a radiationsource configured to continuously irradiate a subject with radiation anda radiation detector configured to detect the radiation transmittedthrough the subject to output a radiographic image. A processor executesbody thickness acquisition processing of acquiring a body thickness ofthe subject measured by a body thickness measurement sensor, settingprocessing of setting a gradation transformation function for use ingradation transformation processing to the radiographic imagecorresponding to the body thickness, image acquisition processing ofacquiring the radiographic image output from the radiation detector, andimage processing of starting the gradation transformation processingwith the set gradation transformation function.

The present disclosure provides an operation program for a processingapparatus that is used for a radioscopy apparatus including a radiationsource configured to continuously irradiate a subject with radiation anda radiation detector configured to detect the radiation transmittedthrough the subject to output a radiographic image. The operationprogram causes a processor to execute body thickness acquisitionprocessing of acquiring a body thickness of the subject measured by abody thickness measurement sensor, setting processing of setting agradation transformation function for use in gradation transformationprocessing to the radiographic image corresponding to the bodythickness, image acquisition processing of acquiring the radiographicimage output from the radiation detector, and image processing ofstarting the gradation transformation processing with the set gradationtransformation function.

According to the technique of the present disclosure, it is possible toprovide a processing apparatus, a method of operating a processingapparatus, and an operation program for a processing apparatus capableof reducing a time needed from when radioscopy is started untilgradation transformation processing becomes appropriate.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments according to the technique of the presentdisclosure will be described in detail based on the following figures,wherein:

FIG. 1 is a diagram showing a radioscopy system;

FIG. 2 is a diagram showing a manner in which a radiation generationunit and a radiation detector reciprocate along a longitudinal directionof an imaging table;

FIGS. 3A and 3B are diagrams showing a manner in which an angle of theradiation generation unit is changed, FIG. 3A shows a manner in whichthe radiation generation unit is directed toward the left, and FIG. 3Bshows a manner in which the radiation generation unit is directed towardthe right;

FIG. 4 is a diagram showing a manner in which radioscopy is performed ona patient in a wheelchair with an imaging table and a post in an uprightstate;

FIG. 5 is a diagram showing a manner in which radioscopy is performed ona patient on a stretcher with the imaging table and the post in theupright state;

FIG. 6 is a diagram showing a manner in which the patient and theperiphery of the patient are imaged with a distance measurement cameraand a distance image representing a distance between a radiation sourceand an object surface is output;

FIG. 7 is a diagram showing a manner in which a body thickness of thepatient is calculated based on a distance between the radiation sourceand a surface of the imaging table and a distance between the radiationsource and a shortest point of a body surface of the patient;

FIG. 8 is a flowchart showing a procedure for setting irradiationconditions;

FIG. 9 is a timing chart showing an operation timing of each unit inradioscopy;

FIG. 10 is a timing chart showing specific content of a detectionoperation;

FIG. 11 is a block diagram of a computer constituting a console;

FIG. 12 is a block diagram showing functions of a CPU and an FPGA of theconsole;

FIG. 13 is a block diagram showing details of an image processing unit;

FIG. 14 is a diagram showing a correction coefficient table;

FIG. 15 is a graph showing a default gradation transformation function;

FIG. 16 is a diagram showing processing of a setting unit in a casewhere the body thickness is comparatively thin;

FIG. 17 is a graph showing a gradation transformation function that isset first in a case where the body thickness is comparatively thin;

FIG. 18 is a diagram showing processing of the setting unit in a casewhere the body thickness is comparatively thick;

FIG. 19 is a graph showing a gradation transformation function that isset first in a case where the body thickness is comparatively thick;

FIG. 20 is a flowchart showing a processing procedure of a processingapparatus;

FIG. 21 is a graph showing the outline of gradation transformationprocessing in the related art;

FIG. 22 is a graph showing the outline of gradation transformationprocessing according to the technique of the present disclosure;

FIG. 23 is a graph showing the outline of the gradation transformationprocessing according to the technique of the present disclosure in acase where the body thickness is changed during an operation;

FIG. 24 is a diagram showing a manner of tomosynthesis imaging;

FIG. 25 is a diagram showing a manner of reconfiguring tomographicimages from a plurality of projection images obtained by tomosynthesisimaging;

FIG. 26 is a flowchart showing a procedure of a second embodiment;

FIG. 27 is a flowchart showing a procedure in the related art as acomparative example; and

FIG. 28 is a diagram showing a radioscopy system comprising a C-arm typeradioscopy apparatus.

DETAILED DESCRIPTION First Embodiment

In FIG. 1 , a radioscopy system 2 comprises a radioscopy apparatus 10and a console 11. The radioscopy apparatus 10 is provided in, forexample, an operation room of a medical facility. The operation room isa room where an operator OP, such as a radiographer or a physician,performs an operation, such as a gastric barium test, cystography, ororthopedic reduction, to a patient P. The radioscopy apparatus 10performs radioscopy to the patient P under operation. The patient P isan example of a “subject” according to the technique of the presentdisclosure.

The console 11 is an example of a “processing apparatus” according tothe technique of the present disclosure, and is provided in, forexample, a control room next to the operation room. The console 11controls the operation of each unit of the radioscopy apparatus 10. Theconsole 11 is, for example, a desktop personal computer, and has adisplay 12 and an input device 13, such as a keyboard or a mouse. Thedisplay 12 displays an imaging order or the like from a radiologyinformation system (RIS). The input device 13 is operated by theoperator OP in designating an imaging menu corresponding to the imagingorder, or the like.

The radioscopy apparatus 10 has an imaging table 20, an operator monitor21, a foot switch 22, and the like. The imaging table 20 is supported ona floor surface of the operation room by a stand 23. A radiationgeneration unit 25 is attached to the imaging table 20 through a post24. The radiation generation unit 25 is constituted of a radiationsource 30, a collimator 31, and a distance measurement camera 32. Aradiation detector 33 is incorporated in the imaging table 20.

The radiation source 30 has a radiation tube 40. The radiation tube 40emits radiation R, such as X-rays or y-rays, and irradiates the patientP lying on the imaging table 20 with the radiation R, for example. Theradiation tube 40 is provided with a filament, a target, a gridelectrode, and the like (all are not shown). A voltage is appliedbetween the filament as a cathode and the target as an anode from avoltage generator 41. The voltage that is applied between the filamentand the target is referred to as a tube voltage. The filament dischargesthermoelectrons according to the applied tube voltage toward the target.The target radiates the radiation R with collision of thethermoelectrons from the filament. The grid electrode is disposedbetween the filament and the target. The grid electrode changes a flowrate of the thermoelectrons from the filament toward the targetdepending on the voltage applied from the voltage generator 41. The flowrate of the thermoelectrons from the filament toward the target isreferred to as a tube current. The tube voltage and the tube current areset as irradiation conditions (see FIG. 8 ) along with an irradiationtime.

The collimator 31 and the distance measurement camera 32 are attached toa lower portion of the radiation source 30. The collimator 31 limits anirradiation field IF of the radiation R generated from the radiationtube 40. For example, the collimator 31 has a configuration in whichfour shield plates formed of lead or the like shielding the radiation Rare disposed on respective sides of a quadrangle, and an emissionopening of the quadrangle transmitting the radiation R is formed in acenter portion. The collimator 31 changes the positions of the shieldplates to change an opening degree of the emission opening, andaccordingly, changes the irradiation field IF.

The distance measurement camera 32 is a camera that measures a distanceto object surface using a time-of-flight (TOF) system. The distancemeasurement camera 32 is an example of a “body thickness measurementsensor” according to the technique of the present disclosure. Thedistance measurement camera 32 is viewed to be substantially as the sameposition as the radiation source 30, more exactly, a focus F of theradiation tube 40 at which the radiation R is generated, as viewed fromthe patient P side. For this reason, the distance measurement camera 32may measure a distance between the radiation source 30 and an objectsurface. The object surface may be, for example, a body surface of thepatient P or a surface of the imaging table 20. A distance between thefocus F and the distance measurement camera 32 may be measured inadvance, and a result obtained by adding the distance measured inadvance between the focus F and the distance measurement camera 32 tothe distance measured by the distance measurement camera 32 may be setas the distance between the radiation source 30 and the object surface.In the example, the distance between the radiation source 30 and thesurface of the imaging table 20 is invariable.

The radiation detector 33 has a configuration in which a plurality ofpixels that are sensitive to the radiation R or visible light convertedfrom the radiation R by a scintillator to generate signal charge arearranged. Such a radiation detector 33 is referred to as a flat paneldetector (FPD). The radiation detector 33 detects the radiation Remitted from the radiation tube 40 and transmitted through the patientP, and outputs a radiographic image 45. The radiation detector 33transmits the radiographic image 45 to the console 11. The radiographicimage 45 is also referred to as a perspective image.

The operator monitor 21 is supported on the floor surface of theoperation room by a stand 46. The radiographic image 45 that is outputfrom the radiation detector 33 and is subjected to various kinds ofimage processing with the console 11 is displayed on the operatormonitor 21 in a form of video in real time.

The foot switch 22 is a switch for the operator OP giving an instructionto start and end radioscopy while being seated in the operation room. Ina case where the operator OP depresses the foot switch 22 with a foot,radioscopy is started. Then, while the operator OP is depressing thefoot switch 22 with the foot, radioscopy is continued. In a case wherethe operator OP releases the foot from the foot switch 22, and thedepression of the foot switch 22 is released, radioscopy ends.

In a case where the foot switch 22 is depressed with the foot of theoperator OP, the filament of the radiation tube 40 is pre-heated, andsimultaneously the rotation of the target is started. After the filamentreaches a specified temperature, and the target is at a specifiedrotation speed, the tube voltage is applied from the voltage generator41, and the radiation R is generated from the radiation tube 40.

As shown in FIG. 2 , not only the post 24 but also the radiationgeneration unit 25 can reciprocate along a longitudinal direction of theimaging table 20 by a movement mechanism (not shown), such as a motor.The radiation detector 33 can also reciprocate along the longitudinaldirection of the imaging table 20 in conjunction with the movement ofthe radiation generation unit 25. The radiation detector 33 is moved toa facing position where the center thereof coincides with the focus F ofthe radiation tube 40. The imaging table 20 is provided with a controlpanel (not shown) for inputting an instruction to move the radiationgeneration unit 25 and the radiation detector 33. The operator OP inputsan instruction through the control panel and moves the radiationgeneration unit 25 and the radiation detector 33 to desired positions.The radiation generation unit 25 and the radiation detector 33 can becontrolled by remote control by a control console (not shown) from thecontrol room.

As shown in FIGS. 3A and 3B, the radiation generation unit 25 can changean angle right and left with respect to the post 24 with a hand of theoperator OP. A changeable maximum angle is, for example, 90° right andleft. The changing of the angle of the radiation generation unit 25 withrespect to the post 24 can be controlled by remote control from thecontrol room.

The imaging table 20 and the post 24 can rotate between a decubitusstate shown in FIGS. 1 and 2 and an upright state shown in FIGS. 4 and 5by a rotation mechanism (not shown), such as a motor. The decubitusstate is a state in which the surface of the imaging table 20 isparallel to the floor surface and the post 24 is perpendicular to thefloor surface. On the contrary, the upright state is a state in whichthe surface of the imaging table 20 is perpendicular to the floorsurface, and the post 24 is parallel to the floor surface. In theupright state, not only radioscopy on the patient P in an uprightposture, but also radioscopy on the patient P in a wheelchair 50 asshown in FIG. 4 can be performed. In the upright state, radioscopy onthe patient P on a stretcher 51 as shown in FIG. 5 can also beperformed. In the case of FIG. 5 , the radiation detector 33 is detachedfrom the imaging table 20 and is set between the patient P and thestretcher 51.

As shown in FIG. 6 , the distance measurement camera 32 images arectangular imaging range SR including the patient P and the peripheryof the patient P, and outputs a distance image 55. The imaging range SRis a range sufficiently wider than a maximum irradiation field MIF ofthe radiation R, and covers the entire maximum irradiation field MIF ofthe radiation R.

The distance image 55 is an image in which an attachment position of thedistance measurement camera 32, that is, a position of the radiationsource 30 is represented as 0 m, as illustrated with a profile 56 of aline L at the center. The distance image 55 has, as a pixel value ofeach pixel, a distance between the radiation source 30 and a surface ofan object in the imaging range SR, such as the patient P or the imagingtable 20.

As shown in FIG. 7 , in a case where the distance radiation source 30(distance measurement camera 32) and the surface of the imaging table 20is D1, and the distance between the radiation source 30 (distancemeasurement camera 32) and a shortest point SP of a body surface of thepatient P is D2, a body thickness BT of the patient P can be calculatedby Expression (1) described below.BT=D1−D2  (1)

As described above, the distance D1 between the radiation source 30 andthe surface of the imaging table 20 is invariable. For this reason, in acase where the distance D2 between the radiation source 30 and theshortest point SP of the body surface of the patient P is derived fromthe distance image 55, the body thickness BT is simply calculated. Inthe case of FIG. 5 where radioscopy is performed on the patient P on thestretcher 51, the body thickness BT is calculated by further subtractinga thickness of the radiation detector 33.

The distance D2 is derived as follows, for example. First, the distanceD1 is invariable and known, and thus, a region of the distance image 55having a distance less than the distance D1 as a pixel value isrecognized as a region of the patient P. Next, a position at theshortest distance in the recognized region of the patient P, that is,the shortest point SP is searched, and a pixel value of the searchedshortest point SP is derived as the distance D2. As in the example, in acase where the distance D1 between the radiation source 30 and thesurface of the imaging table 20 is invariable, the distance D2 betweenthe radiation source 30 and the shortest point SP of the body surface ofthe patient P may be regarded as the body thickness BT.

As shown in FIG. 8 , prior to radioscopy, the console 11 receives theimaging order from the RIS and displays the imaging order on the display12 (Step ST10). In the imaging order, patient identification data (ID)for identifying the patient P, an instruction of an operation by aphysician of a treatment department who issues the imaging order, andthe like are registered. The operator OP confirms the content of theimaging order through the display 12.

The console 11 displays a plurality of kinds of imaging menus preparedin advance on the display 12 in an alternatively selectable form. Theoperator OP selects one imaging menu coinciding with the content of theimaging order through the input device 13. With this, the console 11receives an instruction of the imaging menu (Step ST11). The console 11sets irradiation conditions corresponding to the instructed imaging menuwith reference to an irradiation condition table 60 (Step ST12). Afterselecting the imaging menu, the operator OP performs positioning and thelike of the radiation source 30, the radiation detector 33, and thepatient P, and depresses the foot switch 22 with the foot to startradioscopy. The irradiation conditions have content where theirradiation of the radiation R is performed with an extremely low dosecompared to a case where general radiography is performed.

As shown in FIG. 9 , the radiation source 30 starts the irradiation ofthe radiation R set under the irradiation conditions in synchronizationwith a timing at which the foot switch 22 is depressed with the foot ofthe operator OP, that is, a timing from off to on in the drawing. Theradiation source 30 repeats the irradiation and the stop of theradiation R at an irradiation interval II set in advance while the footswitch 22 is being depressed with the foot of the operator OP. That is,the radiation source 30 continuously irradiates the patient P with theradiation R. The radiation source 30 stops the irradiation of theradiation R in a case where the depression of the foot switch 22 isreleased. The irradiation interval II is variable with, for example,about 0.033 seconds (30 frames per second (fps) as converted into aframe rate) as an upper limit. A sign IT indicates an irradiation timeset under the irradiation conditions.

The radiation detector 33 starts a detection operation insynchronization with an irradiation start timing of the radiation R. Theradiation detector 33 repeats the detection operation while the footswitch 22 is being depressed with the foot of the operator OP, and theirradiation of the radiation R is being performed from the radiationsource 30 in a pulsed manner. With the repetitive detection operationsduring the irradiation of the radiation R, the radiation detector 33outputs the radiographic image 45 at the irradiation interval II.

The radiation detector 33 performs the detection operation even thoughthe depression of the foot switch 22 is released, and the irradiation ofthe radiation R is not performed from the radiation source 30. Theradiation detector 33 repeatedly performs the detection operation in astate in which the irradiation of the radiation R is not performed, at adetection interval DI set in advance. The detection interval DI is atime sufficiently longer than the irradiation interval II of theradiation R, and is, for example, one minute. With the detectionoperation in a state in which the irradiation of the radiation R is notperformed, the radiation detector 33 outputs a radiographic image foroffset correction (hereinafter, referred to as an offset correctionimage) 45O. The radiation detector 33 transmits the offset correctionimage 45O to the console 11.

The distance measurement camera 32 performs an imaging operation of thedistance image 55 in synchronization with a detection operation of theoffset correction image 45O of the radiation detector 33. In otherwords, the distance measurement camera 32 measures the body thickness ofthe patient P in synchronization with a timing at which the radiationdetector 33 outputs the offset correction image 45O.

In FIG. 9 , although an aspect where the irradiation of the radiation Ris performed in a pulsed manner has been exemplified, the presentdisclosure is not limited thereto. An aspect where the irradiation ofthe radiation R is consecutively performed while the foot switch 22 isbeing depressed with the foot of the operator OP may be employed. Evenin an aspect where the irradiation of the radiation R is performed in apulsed manner or an aspect where the irradiation of the radiation R isconsecutively performed, the fact remains that the patient P iscontinuously irradiated with the radiation R.

As shown in FIG. 10 , the detection operation is constituted of astorage operation and a reading operation. The storage operation is anoperation to store signal charge in a pixel, and is started insynchronization with the irradiation start timing of the radiation R.The reading operation is an operation to read the signal charge storedin the pixel and to output the signal charge as the radiographic image45, and is started in synchronization with an irradiation end timing ofthe radiation R.

In FIG. 11 , the computer constituting the console 11 comprises astorage device 65, a memory 66, a central processing unit (CPU) 67, afield programmable gate array (FPGA) 68, and a communication unit 69, inaddition to the display 12 and the input device 13. Such devices andunits are connected to one another through a busline 70.

The storage device 65 is a hard disk drive that is incorporated in thecomputer constituting the console 11 or a connected to the computerthrough a cable and a network. Alternatively, the storage device 65 is adisk array in which a plurality of hard disk drives are mounted. In thestorage device 65, a control program, such as an operating system,various application programs, various kinds of data associated with suchprograms, and the like are stored. A solid state drive may be usedinstead of the hard disk drive.

The memory 66 is a work memory on which the CPU 67 executes processing.The CPU 67 loads a program stored in the storage device 65 to the memory66 to execute processing compliant with the program. With this, the CPU67 integrally controls the operation of each unit of the radioscopyapparatus 10. The communication unit 69 takes charge of communication ofvarious kinds of information with each unit of the radioscopy apparatus10.

In FIG. 12 , in the storage device 65 of the console 11, a firstoperation program 75 and a second operation program 76 are stored. Thefirst operation program 75 and the second operation program 76 are anapplication program that causes the computer constituting the console 11to function as a “processing apparatus” according to the technique ofthe present disclosure. That is, the first operation program 75 and thesecond operation program 76 are an example of an “operation program fora processing apparatus” according to the technique of the presentdisclosure. In the storage device 65, the irradiation condition table 60is also stored.

In a case where the first operation program 75 is activated, the CPU 67of the computer constituting the console 11 functions as a radiationsource controller 80, a collimator controller 81, a distance measurementcamera controller 82, a distance image acquisition unit 83, a detectorcontroller 84, a radiographic image acquisition unit 85, an imaginginstruction reception unit 86, and a display controller 87 incooperation with the memory 66 and the like. In a case where the secondoperation program 76 is activated, the FPGA 68 of the computerconstituting the console 11 functions as an image processing unit 90.The CPU 67 and the FPGA 68 are an example of a “processor” according tothe technique of the present disclosure.

The radiation source controller 80 controls the operation of theradiation source 30 to control the irradiation of the radiation R. Theradiation source controller 80 reads the irradiation conditionscorresponding to the imaging menu selected by the operator OP from theirradiation condition table 60 and sets the read irradiation conditionin the voltage generator 41. The radiation source controller 80 causesthe irradiation of the radiation R from the radiation source 30 throughthe voltage generator 41 under the set irradiation conditions. Theradiation source controller 80 outputs irradiation start and stoptimings of the radiation R to the detector controller 84.

The radiation source controller 80 performs auto brightness control(ABC). As known in the art, the ABC is feedback control where, tomaintain the brightness of the radiographic image 45 within a givenrange, during radioscopy, the tube voltage, the tube current, anirradiation time IT, the irradiation interval II, and the like given tothe radiation tube 40 are finely adjusted based on a brightness value(for example, an average value of brightness values of a center regionof the radiographic image 45) of the radiographic image 45 sequentiallyoutput from the radiation detector 33. With the ABC, the brightness ofthe radiographic image 45 is prevented from being extremely changed dueto body movement or the like of the patient P or the radiographic image45 is prevented from being hardly observed.

The collimator controller 81 controls the operation of the shield platesof the collimator 31 and adjusts the opening degree of the emissionopening formed by the shield plates to an opening degree correspondingto the imaging menu selected by the operator OP. The opening degree ofthe emission opening can also be adjusted by the operator OP through acontrol panel (not shown) provided in the collimator 31 itself.

The distance measurement camera controller 82 controls the operation ofthe distance measurement camera 32. Specifically, the distancemeasurement camera controller 82 makes the distance measurement camera32 perform an imaging operation of the distance image 55 insynchronization with the timing at which the radiation detector 33outputs the offset correction image 45O in a case where the irradiationof the radiation R is not performed.

The distance image acquisition unit 83 acquires the distance image 55from the distance measurement camera 32. The distance image acquisitionunit 83 outputs the distance image 55 to the image processing unit 90.

The detector controller 84 controls the operation of the radiationdetector 33. The detector controller 84 makes the radiation detector 33perform the storage operation in a case where the irradiation of theradiation R is started in radioscopy. The detector controller 84 makesthe radiation detector 33 perform the reading operation in a case wherethe irradiation of the radiation R is stopped in radioscopy. With this,the radiographic image 45 is output from the radiation detector 33.

The detector controller 84 makes the radiation detector 33 perform thedetection operation at the detection interval DI in a case where theirradiation of the radiation R is not performed. With this, the offsetcorrection image 45O is output from the radiation detector 33.

The radiographic image acquisition unit 85 acquires the radiographicimage 45 and the offset correction image 45O from the radiation detector33. That is, the radiographic image acquisition unit 85 takes charge of“image acquisition processing” according to the technique of the presentdisclosure. The radiographic image acquisition unit 85 outputs theradiographic image 45 and the offset correction image 45O to the imageprocessing unit 90.

The imaging instruction reception unit 86 receives an instruction tostart and end radioscopy through the foot switch 22. The imaginginstruction reception unit 86 outputs the received instruction to theradiation source controller 80 and the detector controller 84.

The display controller 87 performs control for displaying theradiographic image 45 subjected to various kinds of image processingwith the image processing unit 90 on the operator monitor 21. Thedisplay controller 87 also performs control for displaying the imagingorder, the imaging menu, and the like on the display 12.

The image processing unit 90 executes various kinds of image processingon the radiographic image 45. For example, the image processing unit 90executes offset correction processing, sensitivity correctionprocessing, defective pixel correction processing, and the like as theimage processing.

The offset correction processing is processing for subtracting theoffset correction image 45O output in a state in which the irradiationof the radiation R is not performed, from the radiographic image 45output by radioscopy in units of pixels. In the offset correctionprocessing, the latest offset correction image 45O most recentlyacquired by the radiographic image acquisition unit 85 and surrounded bya frame of a two-dot chain line in FIG. 9 is used. The image processingunit 90 executes the offset correction processing to remove fixedpattern noise due to dark charge or the like from the radiographic image45.

The sensitivity correction processing is processing for correctingvariation in sensitivity of each pixel of the radiation detector 33,variation or the like in output characteristic of a circuit that readsthe signal charge, and the like based on sensitivity correction data.The defective pixel correction processing is processing of linearlyinterpolating a pixel value of a defective pixel with a pixel value of asurrounding normal pixel based on information of a defective pixelhaving an abnormal pixel value generated during shipment, during aperiodic inspection, or the like.

The image processing unit 90 executes noise reduction processing, suchas recursive filter processing or spatial filter processing, to theradiographic image 45 subjected to, for example, the offset correctionprocessing, the sensitivity correction processing, and the defectivepixel correction processing described above. The recursive filterprocessing is processing of adding the radiographic image 45 outputfurther in the past than the radiographic image 45 to be processed tothe radiographic image 45 to be processed and outputting a result ofaddition. The past radiographic image 45 is multiplied by an appropriateweighting coefficient before addition to the radiographic image 45 to beprocessed. Examples of the spatial filter processing include medianfilter processing using a median filter and Gaussian filter processingusing a Gaussian filter. The image processing unit 90 outputs theradiographic image 45 subjected to various kinds of image processing tothe display controller 87.

As shown in FIG. 13 , the image processing unit 90 has a body thicknessconversion unit 100, a setting unit 101, a gradation transformationprocessing unit 102, and an evaluation unit 103, in addition to therespective units (not shown) that execute various kinds of processing.

The distance image 55 is input to the body thickness conversion unit 100from the distance image acquisition unit 83. As shown in FIG. 7 andExpression (1), the body thickness conversion unit 100 subtracts thedistance D2 between the radiation source 30 and the shortest point SP ofthe body surface of the patient P from the distance D1 between theradiation source 30 and the surface of the imaging table 20 to calculatethe body thickness BT of the patient P. That is, the body thicknessconversion unit 100 takes charge of “body thickness acquisitionprocessing” according to the technique of the present disclosure. Thebody thickness conversion unit 100 outputs the calculated body thicknessBT to the setting unit 101.

The setting unit 101 sets a gradation transformation function 104I foruse first in the gradation transformation processing unit 102 from adefault gradation transformation function 104D corresponding to the bodythickness BT converted by the body thickness conversion unit 100 basedon a distance image 55 acquired immediately before radioscopy is startedand surrounded by a frame of a two-dot chain line in FIG. 9 . That is,the setting unit 101 takes charge of “setting processing” according tothe technique of the present disclosure.

The setting unit 101 refers to a correction coefficient table 105 insetting the gradation transformation function 104I. The correctioncoefficient table 105 is stored in the storage device 65. As shown inFIG. 14 , a correction coefficient α corresponding to the body thicknessBT is registered in the correction coefficient table 105. The settingunit 101 corrects the default gradation transformation function 104D bythe correction coefficient α to generate the gradation transformationfunction 104I. The setting unit 101 outputs the set gradationtransformation function 104I to the gradation transformation processingunit 102.

The gradation transformation processing unit 102 executes gradationtransformation processing on the radiographic image 45 of a first framewith the gradation transformation function 104I set by the setting unit101. That is, the gradation transformation processing unit 102 takescharge of “image processing” according to the technique of the presentdisclosure. The gradation transformation processing unit 102 outputs theradiographic image 45 subjected to the gradation transformationprocessing to the evaluation unit 103. The radiographic image 45subjected to, for example, the offset correction processing, thesensitivity correction processing, and the defective pixel correctionprocessing described above and before being subjected to theabove-described noise reduction processing is input to the gradationtransformation processing unit 102.

The evaluation unit 103 evaluates whether or not the gradationtransformation processing by the gradation transformation processingunit 102 is appropriate (whether or not the gradation transformationfunction 104 is appropriate). The evaluation unit 103 derives, forexample, a spatial frequency-strength characteristic of the radiographicimage 45 after the gradation transformation processing. Then, theevaluation unit 103 evaluates that the gradation transformationprocessing is appropriate in a case where a peak of the strength isequal to or greater than a threshold frequency set in advance, andevaluates that the gradation transformation processing is notappropriate in a case where the peak of the strength is less than thethreshold frequency. The evaluation unit 103 outputs an evaluationresult to the setting unit 101.

In a case where the evaluation result from the evaluation unit 103 hasthe content that the gradation transformation processing is appropriate,the setting unit 101 outputs the gradation transformation function 104set to the radiographic image 45 of a previous frame to the gradationtransformation processing unit 102 as it is. In contrast, in a casewhere the evaluation result from the evaluation unit 103 has the contentthat the gradation transformation processing is not appropriate, thesetting unit 101 resets the gradation transformation function 104 set tothe radiographic image 45 of the previous frame and outputs the resetgradation transformation function 104 to the gradation transformationprocessing unit 102. The setting unit 101 repeatedly performs theresetting of the gradation transformation function 104 until theevaluation result from the evaluation unit 103 has the content that thegradation transformation processing is appropriate.

The image processing unit 90 does not output the radiographic image 45after the gradation transformation processing to the display controller87 until the evaluation unit 103 evaluates that the gradationtransformation processing is appropriate. For this reason, the displaycontroller 87 does not display the radiographic image 45 on the operatormonitor 21 in a form of video until the gradation transformationprocessing becomes appropriate. In other words, the display controller87 starts video display of the radiographic image 45 on the operatormonitor 21 in a case where the gradation transformation processingbecomes appropriate.

As shown in FIG. 15 , the default gradation transformation function 104Dhas a linear shape where an input pixel value and an output pixel valueare in a one-to-one basis relationship.

As shown in FIGS. 16 and 17 , in a case where the body thickness BT iscomparatively thin, the setting unit 101 generates the gradationtransformation function 104I having a characteristic that a range RH_Oof an output pixel value with respect to a range RH_I where an inputpixel value is relatively high increases more than a range RL_O of anoutput pixel value with respect to a range RL_I where an input pixelvalue is relatively low, from the default gradation transformationfunction 104D based on the correction coefficient α. With the gradationtransformation function 104I having such a characteristic, as shown inFIG. 16 in comparison with a representative histogram 110A of theradiographic image 45 in a case where the body thickness BT iscomparatively thin, contrast of a range R_ROI of a pixel valueconsidered to represent an internal structure of the body of the patientP having a relatively high pixel value increases in the radiographicimage 45.

In contrast, as shown in FIGS. 18 and 19 , in a case where the bodythickness BT is comparatively thick, the setting unit 101 generates thegradation transformation function 104I having a characteristic that arange RL_O of an output pixel value with respect to a range RL_I wherean input pixel value is relatively low increases more than a range RH_Oof an output pixel value with respect to a range RH_I where an inputpixel value is relatively high, from the default gradationtransformation function 104D based on the correction coefficient α. Withthe gradation transformation function 104I having such a characteristic,as shown in FIG. 18 in comparison with a representative histogram 110Bof the radiographic image 45 in a case where the body thickness BT iscomparatively thick, contrast of a range R_ROI of a pixel valueconsidered to represent an internal structure of the body of the patientP having a relatively low pixel value increases in the radiographicimage 45. A peak indicated by reference sign PK in FIGS. 16 and 18represents a region of the radiation R that reaches the radiationdetector 33 without being transmitted through the patient P, that is, adirectly irradiated region.

Next, the operation of the above-described configuration will bedescribed referring to a flowchart of FIG. 20 . In a case where thefirst operation program 75 is activated, as shown in FIG. 12 , the CPU67 of the console 11 functions as the radiation source controller 80,the collimator controller 81, the distance measurement camera controller82, the distance image acquisition unit 83, the detector controller 84,the radiographic image acquisition unit 85, the imaging instructionreception unit 86, and the display controller 87. In a case where thesecond operation program 76 is activated, as shown in FIG. 12 , the FPGA68 of the console 11 functions as the image processing unit 90.

As shown in FIG. 8 , prior to radioscopy, the imaging menu correspondingto the imaging order is selected by the operator OP, and accordingly,the irradiation conditions are set in the voltage generator 41 by theradiation source controller 80. The adjustment of the opening degree ofthe emission opening of the collimator 31 is performed by the collimatorcontroller 81. Subsequently, positioning of the radiation source 30, theradiation detector 33, and the patient P is performed by the operatorOP. Thereafter, the foot switch 22 is depressed by the operator OP, andradioscopy is started.

Before radioscopy is started, as shown in FIG. 9 , under the control ofthe distance measurement camera controller 82, the imaging operation ofthe distance image 55 is performed by the distance measurement camera 32in synchronization with the timing at which the radiation detector 33outputs the offset correction image 45O. The distance image 55 istransmitted from the distance measurement camera 32 to the console 11and is acquired with the distance image acquisition unit 83 (StepST100).

As shown in FIG. 13 , the distance image 55 is output from the distanceimage acquisition unit 83 to the body thickness conversion unit 100 ofthe image processing unit 90. In the body thickness conversion unit 100,the body thickness BT is converted from the distance image 55 as shownin FIG. 7 (Step ST110). With this, the body thickness BT is acquired.The body thickness BT is output from the body thickness conversion unit100 to the setting unit 101. Step ST110 is an example of “body thicknessacquisition processing” according to the technique of the presentdisclosure.

As shown in FIGS. 13, and 16 to 19 , the gradation transformationfunction 104I is set corresponding to the body thickness BT by thesetting unit 101 (Step ST120). In this case, the default gradationtransformation function 104D having a linear shape is correctedcorresponding to the body thickness BT, and the gradation transformationfunction 104I having an S-curved shape is generated. The gradationtransformation function 104I is output from the setting unit 101 to thegradation transformation processing unit 102. Step ST120 is an exampleof “setting processing” according to the technique of the presentdisclosure.

In a case where radioscopy is started, as shown in FIG. 9 , theirradiation of the radiation R from the radiation source 30 is performedin a pulsed manner under the control of the radiation source controller80. The detection operation is repeated by the radiation detector 33 insynchronization with the irradiation of the radiation R under thecontrol of the detector controller 84. With this, the radiographic image45 is output from the radiation detector 33. The radiographic image 45is transmitted from the radiation detector 33 to the console 11 and isacquired with the radiographic image acquisition unit 85 (Step ST130).Step ST130 is an example of “image acquisition processing” according tothe technique of the present disclosure.

The radiographic image 45 is output from the radiographic imageacquisition unit 85 to the image processing unit 90. Then, in the imageprocessing unit 90, the offset correction processing and the like usingthe offset correction image 45O is executed to the radiographic image45. By the gradation transformation processing unit 102, the gradationtransformation processing is executed to the radiographic image 45 ofthe first frame with the gradation transformation function 104I set bythe setting unit 101 (Step ST140). The radiographic image 45 subjectedto the gradation transformation processing is output from the gradationtransformation processing unit 102 to the evaluation unit 103. StepST140 is an example of “image processing” according to the technique ofthe present disclosure.

The evaluation unit 103 evaluates whether or not the gradationtransformation processing by the gradation transformation processingunit 102 is appropriate (Step ST150). In a case where evaluation is madethat the gradation transformation processing is appropriate (in StepST150, YES), the radiographic image 45 after the gradationtransformation processing is subjected to the noise reductionprocessing, and then, is output from the image processing unit 90 to thedisplay controller 87. Then, the radiographic image 45 is displayed onthe operator monitor 21 and is provided for observation of the operatorOP under the control of the display controller 87. With this, the videodisplay of the radiographic image 45 is started (Step ST200).

In a case where the evaluation unit 103 evaluates that the gradationtransformation processing is not appropriate (in Step ST150, NO), thesetting unit 101 resets the gradation transformation function 104 basedon the radiographic image 45 of the previous frame (Step ST160). Thereset gradation transformation function 104 is output from the settingunit 101 to the gradation transformation processing unit 102.

Similarly to Step ST130, the radiographic image acquisition unit 85acquires the radiographic image 45 (Step ST170). The radiographic image45 is output from the radiographic image acquisition unit 85 to theimage processing unit 90, and is subjected to the gradationtransformation processing by the gradation transformation processingunit 102 with the gradation transformation function 104 reset by thesetting unit 101 (Step ST180). The processing of Steps ST160 to ST180 isrepeatedly executed while the evaluation unit 103 does not evaluate thatthe gradation transformation processing is appropriate (in Step ST190,NO). In a case where the evaluation unit 103 evaluates that thegradation transformation processing is appropriate (in Step ST190, YES),similarly to a case where determination of YES is made in Step ST150,the radiographic image 45 after the gradation transformation processingis output from the image processing unit 90 to the display controller87, and is displayed on the operator monitor 21 and provided forobservation of the operator OP under the control of the displaycontroller 87. With this, the video display of the radiographic image 45is started (Step ST200). Similarly to Step ST130, Step ST170 is anexample of “image acquisition processing” according to the technique ofthe present disclosure.

As described above, the CPU 67 of the console 11 functions as theradiographic image acquisition unit 85. The FPGA 68 of the console 11functions as the image processing unit 90. The image processing unit 90has the body thickness conversion unit 100, the setting unit 101, andthe gradation transformation processing unit 102. The body thicknessconversion unit 100 converts the body thickness BT from the distanceimage 55 imaged by the distance measurement camera 32 to acquire thebody thickness BT. The setting unit 101 sets the gradationtransformation function 104I for use in the gradation transformationprocessing to the radiographic image 45 corresponding to the bodythickness BT. The radiographic image acquisition unit 85 acquires theradiographic image 45 output from the radiation detector 33 inradioscopy. The gradation transformation processing unit 102 starts thegradation transformation processing with the gradation transformationfunction 104I set by the setting unit 101.

FIG. 21 is a graph 115 showing the outline of gradation transformationprocessing in the related art shown as a comparative example. In therelated art, the default gradation transformation function 104D is setfirst regardless of the body thickness BT. For this reason, there is acase where the default gradation transformation function 104D issignificantly far from an appropriate gradation transformation function104P. In this case, a comparatively long time TL is needed from when thestart of radioscopy is instructed by the foot switch 22 until thegradation transformation processing converges into an appropriate stateand the video display of the radiographic image 45 is started. There isalso case where the default gradation transformation function 104D isexcessively far from the appropriate gradation transformation function104P, the gradation transformation processing does not converge into anappropriate state until a specified time, and an error occurs.

In contrast, as the graph 116 shown in FIG. 22 , in the technique of thepresent disclosure, the gradation transformation function 104Icorresponding to the body thickness BT is set first. A differencebetween the gradation transformation function 104I and the appropriategradation transformation function 104P is slightly small compared to thedefault gradation transformation function 104D. For this reason, a timeTS needed from when the start of radioscopy is instructed by the footswitch 22 until the gradation transformation processing converges intoan appropriate state and the video display of the radiographic image 45is started is considerably reduced compared to the time TL in a case ofFIG. 21 . Accordingly, according to the technique of the presentdisclosure, it is possible to reduce a time needed from when radioscopyis started until the gradation transformation processing becomesappropriate.

In radioscopy, for example, there is a case where the irradiation of theradiation R is stopped once and the posture of the patient P is changedseveral times, such as orthopedic reduction. In a case where the bodythickness BT is frequently changed during the operation in this way, inthe related art, it is necessary to wait for a comparatively long timeuntil the gradation transformation processing converges into anappropriate state and the video display of the radiographic image 45 isstarted, making the operator OP feel stress.

In contrast, in the technique of the present disclosure, as shown ingraphs 116A and 116B of FIG. 23 , even though a posture of the patient Pis changed and the body thickness BT is changed, a long time is notneeded until the gradation transformation processing converges into anappropriate state and the video display of the radiographic image 45 isstarted. For this reason, the operator OP can perform an operationwithout feeling stress.

In the gradation transformation function 104I, as the body thickness BTis thinner, the setting unit 101 increases the range RH_O of the outputpixel value with respect to the range RH_I where the input pixel valuerelatively high, more than the range RL_O of the output pixel value withrespect to the range RL_I where the input pixel value is relatively low.For this reason, it is possible to increase the contrast of the rangeR_ROI of the pixel value considered to represent the internal structureof the body of the patient P in a case where the body thickness BT isthin, in the radiographic image 45, and to provide the operator OP withan easier-to-observe radiographic image 45.

In the gradation transformation function 104I, as the body thickness BTis thicker, the setting unit 101 increases the range RL_O of the outputpixel value with respect to the range RL_I where the input pixel valueis relatively low, more than the range RH_O of the output pixel valuewith respect to the range RH_I where the input pixel value is relativelyhigh. For this reason, it is possible to increase the contrast of therange R_ROI of the pixel value considered to represent the internalstructure of the body of the patient P in a case where the bodythickness BT is thick, in the radiographic image 45, and to provide theoperator OP with an easier-to-observe radiographic image 45.

The setting unit 101 corrects the default gradation transformationfunction 104D corresponding to the body thickness BT to generate thegradation transformation function 104I. Specifically, the setting unit101 generates the gradation transformation function 104I having anS-curved shape from the default gradation transformation function 104Dhaving a linear shape. For this reason, it is possible to simplygenerate the gradation transformation function 104I corresponding to thebody thickness BT.

The distance measurement camera controller 82 makes the distancemeasurement camera 32 measure the body thickness BT of the patient P ina case where the irradiation of the radiation R is not performed. Asdescribed above, in radioscopy, there is a case where the irradiation ofthe radiation R is stopped once and the posture of the patient P ischanged several times, such as orthopedic reduction. For example, in acase where the irradiation of the radiation R is not performed, and in acase where the distance measurement camera 32 is made to measure thebody thickness BT of the patient P, even though the posture of thepatient P is changed while the irradiation of the radiation R is stoppedonce, it is possible to obtain the body thickness BT corresponding tothe changed posture.

The distance measurement camera controller 82 makes the distancemeasurement camera 32 measure the body thickness BT of the patient P insynchronization with the timing at which the radiation detector 33outputs the offset correction image 45O. The timing at which theradiation detector 33 outputs the offset correction image 45O isinevitably a timing at which the irradiation of the radiation R is notperformed. The detection interval DI at which the radiation detector 33outputs the offset correction image 45O is comparatively frequent. Forthis reason, in a case where the distance measurement camera 32 is madeto measure the body thickness BT of the patient P in synchronizationwith the timing at which the radiation detector 33 outputs the offsetcorrection image 45O, it is possible to reliably measure the bodythickness BT before radioscopy.

As a “body thickness measurement sensor” according to the technique ofthe present disclosure, the distance measurement camera 32 that isattached to the radiation source 30 and measures the distance betweenthe radiation source 30 and the body surface of the patient P using theTOF system is used. As the body thickness measurement sensor, a stereocamera that measures a distance to an object from an image imaged withtwo cameras having parallax may be used, instead of the illustrateddistance measurement camera 32. Alternatively, an ultrasound sensor thatemits an ultrasonic wave from an ultrasound transducer to measure adistance to an object based on an ultrasound echo reflected from theobject may be used. The distance measurement camera 32 is morepreferable because the distance between the radiation source 30 and thebody surface of the patient P can be more accurately measured and asimple device configuration can be made, compared to the stereo camera,the ultrasound sensor, or the like.

The timing at which the distance measurement camera 32 is made tomeasure the body thickness BT is not limited to the exemplified timingat which the radiation detector 33 outputs the offset correction image45O. The distance measurement camera 32 may be made to measure the bodythickness BT at regular intervals simply while the depression of thefoot switch 22 is released.

The gradation transformation function 104I is not limited to theillustrated S-curved shape. An S-polygonal line shape may be applied. Ina case of the gradation transformation function 104I having anS-polygonal line shape, a difference in contrast of a portion having aslope of 0 is eliminated and distinction is confused, and thus, thegradation transformation function 104I having an S-curved shape is morepreferable.

The default gradation transformation function 104D is also not limitedto the illustrated linear shape. An S-curved shape may be applied.

Although the distance between the radiation source 30 and the surface ofthe imaging table 20 is invariable, the present disclosure is notlimited thereto. A configuration may be made in which the distancebetween the imaging table 20 and the radiation source 30 is variable.

To rapidly converge ABC by the radiation source controller 80, theirradiation conditions may be changed depending on the body thicknessBT.

The radiographic image 45 may be equally divided into a plurality ofregions, the gradation transformation function 104I or 104 may be setindividually to each region, and the gradation transformation processingmay be executed for each region.

Second Embodiment

In a second embodiment shown in FIGS. 24 to 26 , tomosynthesis imagingis performed in addition to radioscopy.

As shown in FIG. 24 , tomosynthesis imaging is imaging where theradiation source 30 is sequentially moved to a plurality of irradiationpositions IP arranged at equal intervals along the longitudinaldirection of the imaging table 20, the irradiation of the radiation R isperformed from a plurality of focuses F corresponding to the respectiveirradiation positions IP to the radiation detector 33, and theradiographic image 45 (hereinafter, referred to as a projection image45P) is output from the radiation detector 33 each time. Intomosynthesis imaging, the radiation detector 33 is placed at the centerof the irradiation position IP. FIG. 24 shows an example oftomosynthesis imaging where the irradiation of the radiation R isperformed from 15 focuses F1 to F15 corresponding to 15 irradiationpositions IP1 to IP15 centering on an irradiation position IP8, and 15projection images 45P are obtained.

As shown in FIG. 25 , the image processing unit 90 reconfigurestomographic images 45T corresponding to tomographic planes TF1 to TFN ofthe patient P from the projection images 45P obtained throughtomosynthesis imaging shown in FIG. 24 using a known method, such as afiltered back projection method. The image processing unit 90reconfigures the tomographic image 45T with a slice thickness SLT set inadvance. The display controller 87 displays the tomographic images 45Ton the operator monitor 21.

As shown in FIG. 26 , in the console 11, the slice thickness SLTcorresponding to the body thickness BT of the patient P converted fromthe distance image 55 is automatically set with reference to a slicethickness table 500 (Step ST500). In the slice thickness table 500, theslice thickness SLT of a greater value is registered as the bodythickness is thicker. The slice thickness table 500 is stored in thestorage device 65.

After the slice thickness SLT is automatically set, tomosynthesisimaging shown in FIG. 24 is performed (Step ST510). With this, aplurality of projection image 45P corresponding to the respectiveirradiation positions IP are obtained. Then, as shown in FIG. 25 , thetomographic image 45T is reconfigured from the projection image 45P withthe automatically set slice thickness SLT by the image processing unit90 (Step ST520). The reconfigured tomographic image 45T is displayed onthe operator monitor 21 under the control of the display controller 87(Step ST530).

FIG. 27 is a flowchart showing a procedure in the related art as acomparative example. In the related art, the operator OP manually sets aslice thickness SLT through the input device 13 based on a bodythickness BT of a visible aspect of the patient P (Step ST1000). Forthis reason, the operator OP determines whether or not a set value isacceptable as the slice thickness SLT by the tomographic image 45Tdisplayed on the operator monitor 21 (Step ST1100). Then, in a casewhere the set value is not acceptable as the slice thickness SLT (inStep ST1100, NO), the operator OP resets the slice thickness SLT (StepST1200), and the processing of Steps ST520 and ST530 is repeated. A timeof about several minutes is needed in reconfiguring the tomographicimage 45T from the projection image 45P after the slice thickness SLT isreset. Therefore, in the related art, there is a case where a time isneeded to obtain a tomographic image 45T at a desired slice thicknessSLT.

In contrast, in the second embodiment, as shown in FIG. 26 , the slicethickness SLT is automatically set depending on the body thickness BT ofthe patient P converted from the distance image 55. Accordingly, a lotof labor is not needed to manually set the slice thickness SLT unlikethe related art, and a lot of time is not needed until the tomographicimage 45T of a desired slice thickness SLT is obtained.

The technique of the present disclosure may be applied to a radioscopysystem 600 shown in FIG. 28 . The radioscopy system 600 comprises aradioscopy apparatus 601 and a console 602 integrated into theradioscopy apparatus 601. The radioscopy apparatus 601 is a so-calledC-arm type in which a radiation generation unit 604 is attached to oneend of a C-arm 603, and a radiation detector 606 is incorporated in aholder 605 provided in the other end of the C-arm 603. The radiationgeneration unit 604 has a radiation source 607 and a collimator 608. Theradiation source 607 has a radiation tube 609. In FIG. 28 , a footswitch and an operator monitor are omitted.

In a case of the C-arm type radioscopy apparatus 601, normally, toreduce useless exposure to the operator OP, radioscopy is performed inan under-tube posture shown in FIG. 28 in which the radiation source 607is positioned below the patient P and the radiation detector 606 arepositioned above the patient P with a bed 610 sandwiched between theradiation source 607 and the radiation detector 606. For this reason, inthe radioscopy apparatus 601, a distance measurement camera 611 isattached to the holder 605, not the radiation generation unit 604. Inthis case, it is possible to calculate the body thickness BT bysubtracting a distance between the distance measurement camera 611 andthe shortest point of the body surface of the patient P from a distancebetween the distance measurement camera 611 and a surface of the bed610.

In the C-arm type radioscopy apparatus 601, although it is extremelyrare, there is a case where radioscopy is performed in an over-tubeposture in which the radiation source 607 is positioned above thepatient P and the radiation detector 606 is positioned below the patientP. To cope with radioscopy in the over-tube posture, the distancemeasurement camera 611 may be attached to not only the holder 605 butalso the radiation generation unit 604.

Although the patient P is exemplified as the subject, the presentdisclosure is not limited thereto. A pet, such as a dog or a cat, or adomestic animal, such as a horse or cattle, may be a subject.

The hardware configuration of the computer constituting the console 11can be modified in various ways. The console 11 can also be constitutedof a plurality of computers separated as hardware for the purpose ofimproving processing capability and reliability. For example, thefunctions of the respective units 80 to 87 constructed in the CPU 67 andthe function of the image processing unit 90 constructed in the FPGA 68are distributed to two computers. In this case, the console 11 isconstituted of two computers.

In this way, the hardware configuration of the computer of the console11 can be appropriately changed depending on required performance, suchas processing capability, safety, or reliability. Not only hardware butalso an application program, such as the first operation program 75 andthe second operation program 76, can be of course duplicated ordistributed and stored in a plurality of storage devices for the purposeof ensuring safety and reliability.

As the hardware structures of processing units that execute variouskinds of processing, such as the radiation source controller 80, thecollimator controller 81, the distance measurement camera controller 82,the distance image acquisition unit 83, the detector controller 84, theradiographic image acquisition unit 85, the imaging instructionreception unit 86, the display controller 87, the image processing unit90, the body thickness conversion unit 100, the setting unit 101, andthe gradation transformation processing unit 102, and the evaluationunit 103, various processors described below can be used. Variousprocessors include at least one of a programmable logic device (PLD)that is a processor capable of changing a circuit configuration aftermanufacture, such as the FPGA 68, a dedicated electric circuit that is aprocessor having a circuit configuration dedicatedly designed forexecuting specific processing, such as an application specificintegrated circuit (ASIC), or the like, in addition to the CPU 67 thatis a general-purpose processor executing software (first operationprogram 75) to function as various processing units.

One processing unit may be configured of one of various processorsdescribed above or may be configured of a combination of two or moreprocessors (for example, a combination of a plurality of FPGAs and/or acombination of a CPU and an FPGA) of the same type or different types. Aplurality of processing units may be configured of one processor.

As an example where a plurality of processing units are configured ofone processor, first, as represented by a computer, such as a client ora server, there is a form in which one processor is configured of acombination of one or more CPUs and software, and the processorfunctions as a plurality of processing units. Second, as represented bysystem on chip (SoC) or the like, there is a form in which a processorthat implements all functions of a system including a plurality ofprocessing units into one integrated circuit (IC) chip is used. In thisway, various processing units may be configured using one or moreprocessors among various processors described above as a hardwarestructure.

In addition, the hardware structure of various processors is, morespecifically, an electric circuit (circuitry), in which circuitelements, such as semiconductor elements, are combined.

The technique of the present disclosure can also be appropriatelycombined with at least one of various embodiments or variousmodification examples described above. The technique of the presentdisclosure is not limited to the above-described embodiments, andvarious configurations can be of course employed without departing fromthe spirit and scope of the technique of the present disclosure. Inaddition to the program, the technique of the present disclosure extendsto a storage medium that stores the program in a non-transitory manner.

The content of the above description and the content of the drawings aredetailed description of portions according to the technique of thepresent disclosure, and are merely examples of the technique of thepresent disclosure. For example, the above description relating toconfiguration, function, operation, and advantageous effects isdescription relating to examples of configuration, function, operation,and advantageous effects of the portions according to the technique ofthe present disclosure. Thus, it is needless to say that unnecessaryportions may be deleted, new elements may be added, or replacement maybe made to the content of the above description and the content of thedrawings without departing from the gist of the technique of the presentdisclosure. Furthermore, to avoid confusion and to facilitateunderstanding of the portions according to the technique of the presentdisclosure, description relating to common technical knowledge and thelike that does not require particular description to enableimplementation of the technique of the present disclosure is omittedfrom the content of the above description and the content of thedrawings.

In the specification, “A and/or B” is synonymous with “at least one of Aor B”. That is, “A and/or B” may refer to A alone, B alone, or acombination of A and B. Furthermore, in the specification, a similarconcept to “A and/or B” applies to a case in which three or more mattersare expressed by linking the matters with “and/or”.

All of the documents, patent applications, and technical standards inthe specification are incorporated herein by reference to the sameextent that the individual documents, patent applications, and technicalstandards are described specifically and independently.

What is claimed is:
 1. A processing apparatus that is used for aradioscopy apparatus including a radiation source configured tocontinuously irradiate a subject with radiation and a radiation detectorconfigured to detect the radiation transmitted through the subject tooutput a radiographic image, the processing apparatus comprising: atleast one processor, the processor is configured to (1) acquire a bodythickness of the subject measured by a body thickness measurementsensor, (2) set a gradation transformation function for use in gradationtransformation processing to the radiographic image corresponding to thebody thickness, gradation transformation processing processes an inputpixel value which is a pixel value of the radiographic image and outputsas an output pixel value, (3) acquire the radiographic image output fromthe radiation detector, and (4) execute the gradation transformationprocessing with the set gradation transformation function, (5) derive aspatial frequency-strength characteristic of the radiographic imageafter the gradation transformation processing, and (6) in a case inwhich a peak of the spatial frequency-strength characteristic is equalto or greater than a threshold frequency set or calculated in advance,output the radiographic image after the gradation transformationprocessing, and in a case in which the peak is less than the thresholdfrequency, reset the gradation transformation function and repeat theprocess from (3).
 2. The processing apparatus according to claim 1,wherein the processor is configured to, in the gradation transformationfunction, as the body thickness is thinner, increase a range of theoutput pixel value with respect to a range where the input pixel valueis relatively high, more than a range of an output pixel value withrespect to a range where an input pixel value is relatively low.
 3. Theprocessing apparatus according to claim 1, wherein the processor isconfigured to, in the gradation transformation function, as the bodythickness is thicker, increase a range of the output pixel value withrespect to a range where the input pixel value is relatively low, morethan a range of an output pixel value with respect to a range where aninput pixel value is relatively high.
 4. The processing apparatusaccording to claim 1, wherein the processor is configured to correct adefault gradation transformation function corresponding to the bodythickness to generate the gradation transformation function to be set.5. The processing apparatus according to claim 1, wherein the processoris configured to make the body thickness measurement sensor measure thebody thickness in a case where the irradiation of the radiation is notperformed.
 6. The processing apparatus according to claim 1, wherein thebody thickness measurement sensor is a distance measurement camera thatoutputs a distance image representing a distance to a surface of anobject using a time-of-flight system, and the processor is configured toconvert the body thickness from the distance image.
 7. The processingapparatus according to claim 4, wherein the processor is configured togenerate the gradation transformation function having an S-curved shapefrom the default gradation transformation function having a linearshape.
 8. The processing apparatus according to claim 5, wherein theprocessor is configured to make the body thickness measurement sensormeasure the body thickness in synchronization with a timing at which theradiation detector outputs the radiographic image for offset correction.9. A method of operating a processing apparatus that is used for aradioscopy apparatus the method comprising: continuously irradiatingradiation from a radiation source to a subject; and detecting theradiation transmitted through the subject using a radiation detector tooutput a radiographic image, acquiring a body thickness of the subjectmeasured by a body thickness measurement sensor; setting a gradationtransformation function for use in gradation transformation processingto the radiographic image corresponding to the body thickness, gradationtransformation processing processes an input pixel value which is apixel value of the radiographic image and outputs as an output pixelvalue; acquiring the radiographic image output from the radiationdetector; executing the gradation transformation processing with the setgradation transformation function; deriving a spatial frequency-strengthcharacteristic of the radiographic image after the gradationtransformation processing; and in a case in which a peak of the spatialfrequency-strength characteristic is equal to or greater than athreshold frequency set or calculated in advance, output theradiographic image after the gradation transformation processing, and ina case in which the peak is less than the threshold frequency, resettingthe gradation transformation function and repeating the process from theacquiring the radiographic image.
 10. A non-transitory computer-readablestorage medium storing an operation program for a processing apparatusthat is used for a radioscopy apparatus including a radiation sourceconfigured to continuously irradiate a subject with radiation and aradiation detector configured to detect the radiation transmittedthrough the subject to output a radiographic image, the operationprogram causing a processor to execute: (1) body thickness acquisitionprocessing of acquiring a body thickness of the subject measured by abody thickness measurement sensor; (2) setting processing of setting agradation transformation function for use in gradation transformationprocessing to the radiographic image corresponding to the bodythickness, gradation transformation processing processes an input pixelvalue which is a pixel value of the radiographic image and outputs as anoutput pixel value; (3) image acquisition processing of acquiring theradiographic image output from the radiation detector; (4) imageprocessing of executing the gradation transformation processing with theset gradation transformation function; (5) deriving a spatialfrequency-strength characteristic of the radiographic image after thegradation transformation processing; and (6) in a case in which a peakof the spatial frequency-strength characteristic is equal to or greaterthan a threshold frequency set or calculated in advance, output theradiographic image after the gradation transformation processing, and ina case in which the peak is less than the threshold frequency, resettingthe gradation transformation function and repeating the process from(3).